Get substrings from string in C - c

Question

I have such string (it's a string that represents a system path actually):
./home/user/dir1/dir2/
And now, I would like to be able to create presented directory tree, so I need to create home, user, dir1, dir2.
I know how to create dirs in C in Linux, but have troubles with chopping off the string. Basically, what I need now is to have an array of strings:
tmp[0] = "./home/";
tmp[1] = "./home/user/";
tmp[2] = "./home/user/dir1/";
tmp[3] = "./home/user/dir1/dir2/";
and if I will hav such array it would be pretty easy to make presented dir tree but how to split the string in that way?

Answer 1

This is a bit naive but it should get you started. It will handle paths that may or may not have a trailing / and also escaped paths, such as ./home/some\/user/dir1/dir2
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
char path[] = "./home/user/dir1/dir2";
char *start = path;
char *end = start + strlen(path);
while (start < end) {
char *slash = strchr(start, '/');
if (slash) {
if (slash > path && *(slash - 1) == '\\') {
start = slash + 1;
continue;
}
*slash = 0;
}
if (strcmp(start, ".") != 0) {
/* Use 'path' for mkdir here */
/* mkdir(path, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH) or whatever */
printf("going to make %s\n", path);
}
if (!slash) {
break;
}
*slash = '/';
start = slash + 1;
}
return 0;
}

Answer 2

I'd go for Sean's advice as "You should just exec() mkdir -p ... and save yourself the headache."
However if C is necessary, there you go:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define BUF_SIZE 100
int main(){
char s[] = "./home/user/dir1/dir2/";
char** tmp;
int i, j;
int size = 0;
char* token;
/* count the '/' characters */
char c = s[0];
int count = 0;
i = 0;
while (c != '\0'){
if (s[i] == '/')
count++;
i++;
c = s[i];
}
size = i;
/* ready the tmp array */
tmp = (char**)malloc(count);
for (i = 0; i < count; i++){
tmp[i] = (char*)malloc(BUF_SIZE);
for (j = 0; j < BUF_SIZE; ++j)
tmp[i][j] = '\0';
}
/* special treatment for our first tmp[] */
tmp[0][0] = '.';
tmp[0][1] = '/';
i = 0;
/* tokenize the main string */
token = strtok(s, "./");
while (token != NULL){
if (i > 0)
strcat(tmp[i], tmp[i - 1]);
strcat(tmp[i], token);
strcat(tmp[i], "/");
printf("%s\n", tmp[i]);
token = strtok(NULL, "/");
i++;
}
/* clean up */
for (i = 0; i < count; i++)
free(tmp[i]);
getchar();
return 0;
}
The output is:
./home/
./home/user/
./home/user/dir1/
./home/user/dir1/dir2/

Answer 3

I would use strtok to parse the directory names from the string using "/" as the delimiter.
see: http://www.cplusplus.com/reference/cstring/strtok/
Heres how I did it:
#include <stdio.h>
#include <string.h>
// Count the number of times the character appears in the string
size_t countInstances(char* str, char token) {
size_t count = 0;
while(*str) {
if(*str == token) {
count++;
}
str++;
}
return count;
}
int main() {
char path[] = "./home/user/dir1/dir2/"; // strtok might segfault if this is a pointer (rather than an array)
size_t count = countInstances(path, '/');
char** dirs = malloc(sizeof(*dirs) * count);
char* dir;
size_t i = 0;
dir = strtok(path, "/");
while(dir && i < count) {
dirs[i] = dir; // store reference
printf("%s\n",dir);
dir = strtok (NULL, "/");
i++;
}
free(dirs);
return 0;
}
output is:
.
home
user
dir1
dir2